High Temperature Defect Chemistry of Aluminum Oxide.

Ft. Belvoir Defense Technical Information Center APR 1975.

46 p.

See also report dated 1974, N74-29970.

APPROVED FOR PUBLIC RELEASE.

The high temperature defect structure of aluminum oxide was investigated by measurements on single crystals containing known amounts of cobalt. These include high temperature measurements of the conductivity and the emf of concentration cells as functions of oxygen pressure and temperature, and low temperature measurements of optical absorption and electron spin resonance. Analysis of the results leads to a defect model dominated by interstitial aluminum and divalent substitutional cobalt, to parameters of thermodynamic constants regulating the formation of point defects and the oxidation-reduction of cobalt from divalent to trivalent and vice versa, and to the position of levels of cobalt in the forbidden gap. A similar model applies to aluminum oxides doped with iron.

English

January 31, 2011